Dynamic angle of repose

Powder Static angle of repose Hausner ratio Carr s (%) Rank order from dynamic angle of repose 

Many of the empirical flow indicators currently used have been derived from the work of Carr (1965b,c). These diverse test methods have now been collected together in an American Society for Testing and Materials - ASTM D 6393-99 1999 - standard which covers the apparatus and procedures for measuring the properties of free flowing and moderately cohesive bulk solids and which are collectively known as Carr indices . 

Test A - Measurement of Carr angle of repose Test B - Measurement of Carr angle of fall Test C - Calculation of Carr angle of difference Test D - Measurement of Carr loose bulk density Test E - Measurement of Carr packed bulk density Test F - Calculation of Carr compressibility Test G - Measurement of Carr cohesion Test H - Measurement of Carr uniformity Test I - Measurement of Carr angle of spatula Test J - Measurement of Carr dispersibility 

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Most, if not all, velocity measurements in the bulk, other than NMR/MRI, make measurements through dear end-walls of either long or short cylinders. End-walls, because of friction with the particles, change the dynamic angle of repose near the end-wall and can also cause convections in long cylinders with components of velocity in the axial direction [34, 35], NMR/MRI experiments can avoid the end-wall effects by making measurements far from the end-walls in a long cylinder. 

As can be seen in Fig. 9 the powder is placed in the drum and the drum is allowed to rotate. The powder lifts up and when the dynamic angle of repose is exceeded, the powder sample will avalanche downward. The movement of the powder blocks the photocells from obtaining light and a voltage output, which can be related to the avalanching of the powder is recorded (Fig. 9). A set of data for lactose can be seen in Fig. 10. ... 

For a small kiln slope [Pg.26]

The coordinates appropriate to the active layer may be defined in cartesian coordinates with field variables taken with respect to x and y where, from assumption (iv), —Lactive layer at mid-chord of the free surface plane, and L, half of the mid-chord length. If the angle subtended by the boundary interface is the dynamic angle of repose, C, then tan g is the coefficient of dynamic friction and the stresses can be normalized with the gravity term as (Savage and Hutter, 1989)... 

Other relationships based on conventional penetration theory for packed bed have deduced that Nu = 2 i -JPe and for low Peclet numbers to the order of 10, Tscheng and Watkinson (1979) deduced an empirical correlation, where Nu = 11.6 x7e°. Any of these would suffice in estimating the wall-to-bed heat transfer coefficient as functions of the kiln s rotational speed, w, and the dynamic angle of repose, The calculated values of Nusselt numbers using Perron and Singh s... 

The simplest method to indicate the flowability of bulk powders is to use any technique that measures the static angle of a heap of powder - angle of repose - using either the Carr s angle of repose equipment (Figure 1.9) or a simple apparatus (Figure 1.15). A dynamic angle of repose can now be measured with an Aero-Flow Analyzer. 

M.G. Kleinhans, H. Markies, S.J. de Vet, A.C. in t Veld, and F.N. Postema. Static and dynamic angles of repose in loose granular materials under reduced gravity. Journal of Geophysical Research Planets, 116(E11), 2011. 

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